Many HIV-infected patients have received and continue to receive partially suppressive antiretroviral therapy due to the lack or inaccessibility of drugs that can lead to complete suppression of viral activity. The main danger of this tactic is the loss of therapeutic alternatives in these patients due to the continuous evolution of the virus and its development of drug resistance.

In a study by N. Hatano et al. (United States), data from 106 patients who were continuously receiving antiretroviral therapy with incomplete suppression of HIV activity for 120 days or more, the plasma RNA load of HIV in which was greater than 500 copies / ml, and in which more than one mutation has been determined that has caused resistance to the virus. Phenotypic and genotypic HIV resistance tests were tested every 4 months.

All patients included in the study were examined on average 3 times over a period of 11.3 months. According to the results, at the end of 1 year of observation, 23% and 18% of patients have developed at least 1 new mutation, which causes resistance to nucleoside analogues and to protease inhibitors. 30% lost the phenotypic equivalent of a sensitive drug during the indicated period. A smaller number of mutations in general at the start of the study was an important prognostic factor in the development of a new mutation, which determines resistance to nucleoside analogs (p = 0.01). The probability that the existing mutation is no longer determined by sequencing after 1 year is 32%. In addition, the frequency of changes in codons which are not responsible for the development of resistance was higher than that of the codons which determine the resistance of the virus to drugs.

Thus, HIV-infected patients who have received and continue to receive a partially suppressive antiretroviral regimen are at some risk of losing treatment alternatives, particularly when the virus initially exhibits a small number of mutations. Since the mutations leading to the development of resistance change over time, the results of a single test to identify them cannot be considered representative of all the mutations that have developed during antiretroviral therapy.